Process of producing positive images

ABSTRACT

A stable positive image having high contrast is formed in a dry system without the necessity of heat treatment by subjecting a light-developable silver halide light-sensitive material having a layer of silver halide grains having occuluded therein bismuth ions and containing a mercaptan compound to an intense imagewise exposure in a short period of time and then subjecting the light sensitive material to an overall uniform exposure.

United States Patent n91 llkenoue et al.

[ 1 Dec. 3, 1974 1 PROCESS OF PRODUCING POSITIVE IMAGES [75] Inventors: Shinpei lkenoue; Eiichi Mizuki, both of Saitama, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

' Kanagawa, Japan 22 Filed: Nov. 8, 1972 21 Appl. NO.I 304,879

[30] Foreign Application Priority Data 3,418,122 12/1968 Colt 96/63 3,447,927 Bacon et 211...: 96/108 3,531,291 9/1970 Bacon et a1 96/108 3,547,647 12/1970 Bacon et a1 l 96/108 3,615,511 10/1971 Cole: 96/63 3,655,390 4/1972 Overman 96/64 3,690,891 9/1972 Spence et a1. 96/108 T881,009 12/1970 Tinney .1 96/108 T882,022 l/1971 Fumia et a1 96/108 1 Primary Examiner-David Klein Assistant Examiner-Edward C. Kimlin Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [5 7 ABSTRACT A stable positive image having high contrast is formed in a dry system without the necessity of heat treatment by subjecting a light-developable silver halide lightsensitive material having a layer of silver halide grains having occuluded therein bismuth ions and containing a mercaptan compound to an intense imagewise exposure in a short period of time and then subjecting the light sensitive material .to an overall uniform exposure;

30 Claims, No Drawings PROCESS OF PRODUCING POSITIVE IMAGES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a process of forming a positive image, and more particularly it relates to a process of forming a positive image by subjecting a light-developable silver halide light-sensitive material to a specific treatment.

2. Description of the Prior Art Recently, silver halide light-sensitive materials which can be processed in a dry system have been actively sought by theart. However, conventional silver halide print out materials and light-developable silver halide print out materials generally provide negative images. That. is, typical conventional light-developable lightsensitive materials yield a negative image upon exposure to intense light for a short period of time followed by uniform exposure (see, e.g., Korematsu and Sakai; Journal of the Society of Photographic Science and Technology of Japan; 31, 181-188 (1968).

However,'there are several exceptionsOnce such exception is alight-sensitive material produced using a silver halide emulsion prepared in the presence of bismuth nitrate and having incorporated therein stannous chloride as a halogen acceptor (a print out'sensitizer'). When the light-sensitive material is subjected to an intense imagewise exposure for a short period of time and then to an overall exposure, a positive image is obtained (see, e.g., Sakai et al, Journal of the Society of Photographic Science and Technology of Japan; 30, 164-172 (1967)). However, since .in such a lightsensitive material the stabilization of the exposed portions at imagewise exposure is insufficient, it is impossible to maintain the image for a long period of time under ordinary daylight conditions. Further, the contrast of the image, i.e., the density differencebetween unexposed portions and exposed portions is insufficient in such a light-sensitive material. Furthermore, the sensitivity of the light-sensitive material is about l/l,000 that of light-sensitive materials usually used for forming negative images. Accordingly, a light-sensitive material of the aforesaid type is not suitable for practical purposes.

In Japanese Patent No. 32,036/1970, there is described a light-sensitive material having a photographic emulsion layer containing a silver halide emulsion prepared in an acid media in the presence of tri-valent metal ions and having incorporated therein a halogen acceptor in an amount of 0.01-100 mole percent (based on the silver halide). Further, in Japanese Patent No. 10,551/1970, there is described a dry system using the such a light-sensitive material. According to the dry system, the light-sensitive material is subjected to imagewise 'exposure to form a latent image, is heated to at least 300F (about 150C) to control the printout of unexposed portions, and then is uniformly exposed. This dry system, however, requires a heat treatment as a necessary step.

SUMMARY OF THE INVENTION An object of this invention is to provide a process of obtaining a stable positive image.

Another object of this invention is to provide a process of forming a positive image of high contrast.

- acceptor.

That is to say, the light-sensitive material used in this invention has the following features: the light-sensitive material is a light-developable silver halide lightsensitive material having a photographic emulsion layer of a silver halide emulsion containing silver halide grains which have been prepared by precipitation in the presence of bismuth ions or a bismuth compound to occlude bismuth ions therein, and which have incorporated therein at least one mercaptan compound represented by the following general formula wherein X represents an oxygen atom, a sulfuratom, a selenium atom, or NR; R represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group; and D represents an o-phenylene group, a substituted o-phenylene group, a 1,2-naphthylene group, a substituted 1,2-naphthylene group, a 2,3-napthylene group, or a substituted 2,3- naphthylene group.

The substituents in. the alkyl group, aryl group, ophenylene group, 1,2-naphthylene group or 2,3- naphthylene group may be electron-donatingor electron-accepting groups. Substituents having a Hammetts substituent constant of from -0.68O to +1.30 may be present in the above alkyl group, aryl group, 0- phenylene group, 1,2-naphthylene group or 2,3- naphthylene group. Preferred substituents are described in detail at a following point.

The mercaptan compound represented by the abov general formula can also be expressed by the following general formula wherein X represents an oxygen atom, a sulfur atom, a selenium atom, or NR R, and R each represents a hydrogen atom, a halogen atom, a nitro group, an alkyl group, a substituted alkyl group, a carboxyl group, an acyl group, an aryl group, an alkoxyl group, an alkoxycarbonyl group, a sulfo group, an o-phenylene group, or a substituted o-phenylene group; R represents an alkyl group, a substituted alkyl group, or an aryl group.

Preferred examples of such substituents are, for the alkyl group, substituents such as a halogen atom, an acyl group, an aryl group, an alkoxyl group, etc.; for the o-phenylene group substituents such as a halogen atom, a nitro group, an alkyl group, a carboxyl group, an amyl group, an aryl group etc.

DETAILED DESCRIPTION OF THE INVENTION In the above general formula, the substituted or unsubstituted alkyl group or the alkoxyl group has 1-12 carbon atoms, preferably 1-8 carbon atoms. The acyl group and the alkoxycarbonyl group in the formulae also have l-12 carbon atoms, preferably 1-8 carbon atoms.

The aryl group in the above general formula is a phenyl group or a naphthylene group which may have subsituents such as are exemplified above, e.g., an alkyl group, a halogen atom, an acyl group, etc. Also, the ophenylene group may have an substituents such as are exemplified above, e.g., an alkyl group, a halogen atom, an acyl group, etc.

The precipitated silver halide is formed in an aqueous solution of a hydrophilic colloid containing a bismuth compound which provides bismuth ions. Any bismuth compound which serves as a source of bismuth ions and which does not have an harmful effect on the emulsion may be used in the present invention, there being no other substantial limitation on the selection of the bismuth compound which is used to provide the bismuth ions. Since inorganic bismuth compounds are commonly available at reasonable cost, these are most commonly used. The bismuth compound used need not be completely soluble, but since substantially completely soluble materials are easily available they are often used. The bismuth compound used should preferably have a water-solubility greater than 10' mol/liter at a pH 2. Examples of the bismuth compound incorporated in the aqueous solution of the hydrophilic colloid are inorganic bismuth compounds such as bismuth nitrate, bismuth sulfate, bismuth oxide, bismuth chloride, bismuth bromide, and bismuth iodide, and organic bismuth compounds such as bismuth locate, bismuth oleate, bismuth oxalate and bismuth sodium triglycollamate.

The amount of the bismuth compound added to the aqueous solution of the hydrophilic colloid is in the range of 10 to 2.5 mole percent, preferably 5 X to 10 mole percent, per mole of silver halide. The pH of the aqueous solution of the hydrophilic colloid is generally in the range of l-lO, preferably lower than 6.

The bismuth compound should be added prior to the completion of precipitation, and the mercaptan added after precipitation is completed. The mean given size of the silver halide emulsion is usually less than about 5 microns, preferably in a range of from 0.01 to 2 microns. The grain size of the emulsion is not overly important in the present invention, and the mean grain size can vary substantially. Mean grain size is determined by making a histogram of a 1,000 2,000 grain sample and determining the peak value, which represents the mean grain size.

It is important during the production of the lightsensitive material used in this invention to correctly select the kind of the compound to be incorporated in the silver halide emulsion. That is to say, all compounds accelerating print out are not always used in general for the light-sensitive materials. More specifically, when the mercaptan compounds represented by the abovementioned general formula are used, light-sensitive materials capable of providing stable images of excellent quality can be obtained.

Typical examples of mercaptan compounds of the heretofore described general formula used in the lightsensitive materials of this invention are specifically illustrated below:

2-mercaptobenzothiazole,

2-mercaptobenzimidazole,

Z-mercaptobenzoxazole,

2-mercaptobenzoselenazole,

2-mercapto-4-methylbenzimidazole,

2-mercaptol ',2'-naphthoimidazole,

2-mercapto-5-methylbenzimidazole,

Z-mercaptol -methylbenzimidazole,

5-carboxy-2-mercaptobenzimidazole,

2-mercapto-5-t-octylbenzothiazole, 2-mercapto-5-dodecylbenzothiazole, 2-mercapto-5-nitrobenzimidazole, 2-mercapto-4-methylbenzothiazole, 2-mercapto--methylbenzothiazole, 6-ethyl-2-mercaptobenzothiazole, 2-mercapto-4,6-dimethylbenzothiazole, 6-fluoro-2-mercaptobenzothiazole, 6-chloro-2-mercaptobenzothiazole, 4-bromo-2-mercaptobenzothiazole, 6-iodo-2-mercaptobenzothiazole, 2-mercapto-6-nitrobenzothiazole, 6-ethoxy-2-mercaptobenzothiazole, 6-chloro-4-methyl-2-mercaptobenzothiazole,

S-chloro-2-mercapto-6-nitrobenzothiazole,

6-phenyl-2-mercaptobenzothiazole,

2-mercapto-5-methylbenzoxazole, 2-mercapto-4,6-dimethylbenzoxazole, 5-chloro-2-mercaptobenzoxazole, 5-phenyl-Z-mercaptobenzoxazole, 2-mercapto-S-nitrobenzoxazole, and 2-mercapto-S-sulfobenzimidazole.

It is known that the mercaptan compounds recited above have a strong co-action with a silver halide. This co-action is between the mercapto group of the mercaptan compound and the silver ions of the silver halids. In order for the mercaptan compounds described above to be effective be in the light-sensitive material of this invention, the presence of the aromatic nucleus in the above-mentioned general formula is necessary.

However, the effectiveness of the mercaptan com pound as the additive for the light-sensitive material is not lost even if the properties of the aromatic nucleus of the compound are changed by the introduction of an electron accepting group or an electron donating group on the aromatic nucleus. The amount of the mercaptan compound is usually present in an amount of from 0.05 25 mole percent based on the moles of the silver halide.

As mentioned above, the aforesaid mercaptan compound adsorbs well onto the silver halide grains and thus the optimum amount of the mercaptan compound will depend upon the surface area of-the silver halide grains, i.e., the grain size of the silver halide grains.

For instance, when the mean grain size of the silver halide grains in the silver halide emulsion is about 0.1 micron, the amount of the mercaptan compound is usually in the range on the moles of 0.1 15 mole percent, preferably l-5 mole percent, based on the moles of silver halide in the emulsion.

The silver halide emulsion thus obtained is applied to a proper support. Any support may be used in the present invention as is used for ordinary negative photo- The silver halide, or mixed silver halide, used is not overly critical, nor is the hydrophilic colloid used. On

the contrary, positive systems as are used in the prior art can be processed with excellent results in the present invention. The most preferred systems are, however, those wherein the silver halide contains at least 50 mole percent silver bromide where gelatin is the hydrophilic binder, for example, silver bromide, silver chlorobromide, silver iodobromide, though materials such as silver chloroiodide may also be used.

Other natural and synthetic hydrophilic binders, or mixtures thereof can, of course, be used, e.g., modified gelatins, polyvinyl alcohol, agar-agar etc.

Y The dry processing system of this invention applied to the described light-sensitive materials is as follows. That is to say, by subjecting the afore-mentioned lightsensitive material to highly intense imagewise exposure for a short period of time and thensubjecting it to an overall exposure, a stable positive image can be obtained. In order to obtain a positive image, it is quite important to correctly select the exposure time of the imagewise exposure. More specifically, when the exposure time is too long, it is impossible to obtain a positive image by the subsquent uniform exposure even if the amount of subsequent exposure is increased. The first imagewise exposure must be an exposure of short duration by a light source of high intensity which includes radiation capable of forming a latent image in the silver halide emulsion layer of the light-sensitive material. It

is prefered that the illumination of theexposure be larger than 15,000 lux and the exposure periodbe shorter than second, i.e., higher than 150 CMS. Due to practical limitations, i.e.,cost of apparatus'used to obtain such exposures, the imagewise exposure will usually be at less than 10 lux, though greater exposures may, of course, be used. Again, because of practical cost limitations for the apparatus used, usually imagewise exposure will be for a time greater than 10' seconds. Also, the exposure amount may be to an extent of forming a latent image, and after imagewise exposure a visible image cannot be observed.

The overall exposure after the imagewise exposure is conducted by a light source which includes radiation capable of printing out a silver halide emulsion. Practical examples of such radiation are day light and radiation from a tungsten lamp, afluorescent lamp, a mercury lamp, a xenon lamp, etc. The exposure is preferably higher than 54,000 CMS. For most common uses to which direct positive emulsions are put exposure will at less than about 10 CMS, usually less than about 5 X 10 6 CMS. 7

The portions exposed at the imagewise exposure will have been stabilized but the unexposed portions will not have been stabilized-Thus, the portions unexposed at the imagewise exposure are selectively colored by this invention provides an extremely stable positive imprinting out at the overall exposure, and a stable positive image is obtained.

A conventional general light-developable lightsensitive material provides a negative image by an intense imagewise exposure for a short period of time and an overall exposure, but the light-sensitive material of age.

Furthermore, in the present invention, a heat treatment is not necessary. However, by heating after the imagewise exposure for of a short period of time, the

contrast of the positive image (the density difference between the unexposed portions and the exposed portions at imagewise exposure) obtained by the overall exposure can be improved.

For instance, by bringing the light-sensitive material imagewise exposed into contact with a plate heated to a temperature higher than C for longer than 10 seconds, the contrast of the positive image obtained by the subsequent overall exposure is improved. More preferably, contact is with a plate heated to a temperature higher than 170C ,for a period of longer than 10 seconds. On the other hand, a substantial improvement due to heating is often not observed if heating is at conditions less severe than 70C for 1 second, so usually either a higher temperature and/or greater time will be used. General conditions most commonly used are C for 10 seconds. To avoid the necessity for careful observation of the heating step, usually heating at 280C for 60 seconds will be the maximum needed, and seldom will heating at conditions more severe than heating at 250C for 90 seconds be used.

The upper limits of the heating temperature and heating time are only limited by the destruction and degradation of the binder for the silver halide emulsion layer, and such upper limits are easily determined.

The invention will now be illustrated in greater detail by the following non-limitative examples.

EXAMPLE 1 After adjusting the pH of an aqueous 3 percent by weight gelatin solution to 2.0 with nitric acid, bismuth nitrate was added to the solution in an amount of 2.5 X 10' mole percent based on the silver halide which was to be formed, and then the temperature of the solution was adjusted to 60C. By simultaneously adding to the aqueous gelatin solution containing the bismuth ions an aqueous solution of silver nitrate and a mixture of an aqueous potassium bromide solution and an aqueous sodium chloride solution in a gradual manner, a sil ver chlorobromide emulsion (containing 5 mole percent chloride and mole percent bromide) was prepared. This emulsion was designated Emulsion A. Precipitation was conducted by mixing a 2N aqueous AgNO solution with a 2N aqueous halogen solution .(KBr/NaCl mixture) at a constant rate over a 20 min ute period.

A silver halide emulsion was then prepared following the above procedure except that bismuth nitrate was not added to the aqueous gelatin solution. This emulsion was designated Emulsion B.

After adding to Emulsion A and Emulsion B a methanol solution of Z-mercaptobenzoselenazole in an amount sufficient to provide 2.5 mole percent 2- mercaptobenzoselenazole based on the silver halide, the resultant silver halide emulsions were applied to separate glass plates to provide a coating layer amoun of 30 mg/lOO cm as silver.

Furthermore, as control samples, emulsions identical to Emulsion A and Emulsion B were formed except no 2-mercaptobenzoselenazole was added thereto. There were separate applied to glass plates to provide a coating layer of 30 mg/l cm as silver.

Each of the four samples prepared above was imagewise exposed through an optical wedge having a density difference of 0. l for seconds by means of an Edgerton, Germeshausen and Grien Mark Vll sensitometer. The amount of exposure was 5,000 CMS at the first step of the optical wedge. After the imagewise exposure, no visible image was observed. Then, each of the samples was subjected to overall exposure for 3 minutes by means of a fluorescent lamp of watts at an illumination of 1,800 lux at the surface of the element. In the Emulsion A sample containing 2- mercaptobenzoselenazole, the unexposed portions at the imagewise exposure were selectively printed out after about 30 seconds of overall exposure and began to color blue. After about 90 seconds of overall exposure a distinct positive image was obtained. The portions exposed at the imagewise exposure hardly changed by the overall exposure.

The difference in reflection density between the unexposed portions and the exposed portions at the imagewise exposure after three minutes of overall exposure was 0.22. Further, the image of the optical wedge could be discriminated in 10 steps. The exposure amount at the first step was 5,000 CMS, as mentionedabove, and the exposure amount of the tenth step was 1 60 CMS. The positive image thus obtained was quite stable to ordinary daylight. On the other hand, the other three comparison samples gave no visible image upon overall exposure.

EXAMPLE 2 Among the samples shown in Examples 1, the Emulsion A sample having incorporated therein 2- mercaptobenzoselenazole was imagewise exposed to a light source at various illuminations at a substantially constant exposure amount (3,000 5.000 CMS).

In this Example an EGG sensitometer as described in Example 1 was employed when the exposure period was 10 seconds, 10 seconds, or 10' seconds, while a tungsten .lamp controlled by means of a filter to a 5,400 K color temperature was employed when the exposure period of time was 1 second or 10 seconds. The conditions of overall exposure after imagewise exposure were the same as in Example 1.

The difference (AD) in reflection density between the unexposed portions and the exposed portions at imagewise exposure is shown in Table 1.

. As shown in the above table, where the exposure period for the imagewise exposure was one second or more, a good positive image was not obtained. Usually a AD value greater than 0.05, preferably greater than 0.1, is indicative of a good positive image.

EXAMPLE 3 After adding 2-mercaptobenzothiazole to a silver halide emulsiorthaving the same composition as Emulsion A in Example 1 in an amount of 2.5 mole percent based on the silver halide, the resultant silver halide emulsion was applied to a glass plate in a thickness of 30 mg/ l 00 cm as silver. When the sample was subjected to imagewise exposure (5,000 CMS) for 10' seconds by means of an EGG sensitometer and then to an overall exposure from a fluorescent lamp of 20 watts (1,800 lux), an image began to appear after about 15 seconds and a good positive image was obtained after 60 seconds. The difference in reflection density after subjecting the sample to overall exposure for 3 minutes was 0.17.

Samples containing Z-mercaptobenzoxazole or 2- mercaptobenzimidazole in place of 2-mercaptobenzothiazole were prepared as above and exposed as above. Results similar to those obtained with 2-mercaptobenzothiazole were obtained.

EXAMPLE 4 A silver halide emulsion was prepared by the same conditions as in the case of preparing Emulsion A in Example 1 except that the pH of the emulsion was adjusted to 6. This silver halide emulsion was designated Emulsion C. After adding 2-mercaptobenzothiazole to the silver halide emulsion in an amount of 2.5 mole percent based on the silver halide, the emulsion was applied to a glass plate at a thickness of 30mg/l00 cm as silver. When the sample was processed under the same conditions as in Example 3, a stable positive image having a reflection density difference of 0.08 was obtained.

Another silver halide emulsion was also prepared under the same conditions as above except the pH of the emulsion was adjusted to 8. When the sample was processed under the same conditions as above, a stable image was also obtained.

EXAMPLE 5 Using a element formed as in Example 3 and following the procedure of Example 3, the sample (additive: 2-mercaptobenzothiazole) was brought into contact with an heated iron plate between imagewise exposure and overall exposure. The differences in reflection density when the temperature of the iron plate and the heating period of time were varied is shown in Table 2 by the AD figure. The conditions for imagewise exposure and overall exposure were the same as in Example From the above table, it can be seen that the value of AD generally increases when a heat treatment is used.

EXAMPLE 6 After adding to a silver halide emulsion having the same composition as Emulsion A in Example 1 chloro2-mercaptobenzimidazole in an amount of 2.5

mole percent based on the silver halide, the resultant silver halide emulsion was applied to a glass plate at a thickness of 30 mg/ 100 cm as silver. When the sample thus prepared was processed under the same conditions as in Example 3, a good positive image having a difference in reflection density of 0.21 was obtained.

Similar positive images were obtained when the same procedure as above was conducted adding, in place of 5-chloro-2-mercaptobenzimidazole, 2-mercapto-5- methylbenzimidazole, 5-carboxy-2- mercaptobenzimidazole, 5-chloro-2- mercaptobenzthiazole, 2-mercapto-6- nitrobenzothiazole or 6-ethoxy-2-mercaptobenzothiazole.

EXAMPLE 7 Following the procedure of Example 1, a silver bro mide emulsion, a silver chloride emulsion, and a silver iodobromide emulsion (5 mole percent silver iodide) was prepared in the presence of bismuth nitrate in an amount as recited in Example 1. After adding to each of those silver halide emulsions 2-mercaptobenzothiazole in an amount of 2.5 mole percent based on silver halide, the resultant silver halide emulsion was applied to a support at a thickness of 30 mg/lOO cm as silver. When each of the samples was processed under the same conditions as in Example 3, a good positive image was obtained in each case.

COMPARISON EXAMPLE A comparison sample was prepared by adding to a silver halide emulsion having the same composition as Emulsion A prepared in Example 1 14 mole percent, based on the silver halide, of stannous chloride instead of the mercapto compound. Addition was in accordance with the teachings of Journal of the Society of Photographic Science and Technology of Japan," 31, 181-188 (1968). The silver halide emulsion was applied to asupport as in'Example 1. Another comparison sample was prepared by adding to a silver halide emulsion having the same composition as that of the Emulsion A in Example 1, 2.5 mole percent based on the silver halide of dithiourazole hydrazine salt instead of the mercapto compound (as used in the examples of Japanese Patent Publication No. 32,036/1970 and lapanese Patent Publication No. 10,551/1970). The silver halide emulsion was then applied to a support.

For the purpose of comparison, a sample of this invention was prepared by adding to a silver halide emulsion having the same composition as Emulsion A in Example l 1.5 mole percent, based on the silver halide, of Z-mercaptobenzothiazole. This emulsion was then applied to a support.

The coating amounts used in forming each sample were the same as in Example 1. Wheneach sample was processed under the same conditions as in Example 1, the sample containing stannous chloride and the sample containing dithiourazole hydrazine salt gave positive images but the portions exposed at the imagewise exposure were insufficient in stability, and thus the images were poor in stability. On the other hand, the sam- Table 3 Additive v AD Overall exposure Overall exposure for 3 minutes for 3 hours Stannous chloride 0.10 0.08

Dithiourazole hydrazine salt 0.07 0.06

Z-Mercaptobenzothiazole 0.24 0.45

As is clear from the above results, in the sample containing Z-mercaptobenzothiazole no image-fading was observed. On the contrary, the image became clearer.

Moreover, the reflection density of the background (the areas exposed at imagewise exposure) increased by the overall exposure of 3 hours to 0.19 in the case of using stannous chloride and to 0.25 in the case of using dithiourazole hydrazine salt. On the other hand, the reflection density increased to only 0.06 in the case of using Z-mercaptobenzothiazole.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can .be made therein without departing from the spirit and scope thereof.

What is claimed is:

1. A process of forming positive images which comprises subjecting a light-developable silver halide lightwherein X represents an oxygen atom, a sulfur atom, a

V selenium atom, or -NR; R represents a hydrogen atom, an alkyl group, a substituted alkyl group, a substituted alkyl group, a substituted aryl group, or an aryl group; and D represents an o-phenylene group, a substituted o phenylene group, a 1,2-naphthylene group, a substituted 1,2-naphthylene group, a 2,3-naphthylene group, or a substituted 2,3-naphthylene group.

2.. A process of forming positive images as set forth in claim 1 wherein said mercaptan compound is represented by the formula:

J SH

wherein X represents an oxygen atom, a sulfur atom, a selenium atom, or -NR R, and R each represents a hydrogen atom, a halogen atom, a nitro group, an alkyl group, a substituted alkyl group, a carboxyl group, an acyl group, an aryl group, an alkoxyl group, an alkoxycarbonyl group, a sulfo group, an o-phenylene group, or a substituted o-phenylene group; and R represents an alkyl group, a substituted alkyl group, or an aryl group.

3. A process of forming positive images as set forth in claim 1 wherein the exposure time for the imagewise exposure of high illumination is less than 10 second.

4. A process of forming positive images as set forth in claim 1 wherein the amount of the overall exposure is larger than 54,000 CMS.

5. A process of forming positive images as set forth in claim 1 wherein the amount of said mercaptan compound is from 0.05 to 25 mole percent based on the silver halide in the silver halide emulsion.

6. A process of forming positive images as set forth in claim 1 wherein the silver halide has a grain size less than about 5 microns.

7. A process of forming positive images as set forth in claim 5 wherein the bismuth compound is present in an amount of from to 2.5 mole percent, per mole of silver halide.

8. A process of forming positive images as set forth in claim 1 wherein subsequent to imagewise exposure but prior to overall exposure the element is heated at a temperature of at least 70C for at least 1 second.

9. A process of forming positive images as set forth in claim 8 wherein the heating is for at least 10 seconds.

10. A process of forming positive images as set forth in claim 9 wherein the heating is at a temperature less than 250 to 280C for a time less than 90 seconds to 60 seconds.

11. A process of forming positive images as set forth in claim 1 wherein the silver halide comprises at least 50 percent silver bromide.

12. A process of forming positive images as set forth in claim 1 where any substituted R or substituted D has a substituent with a Hammetts substituent constant of from 0.680 to +1.30.

13. A process of forming positive images as set forth in claim 2 wherein the substituent on the substituted alkyl group is a halogen atom, an acyl group, an aryl group or an alkoxyl group, and the subsituent on the substituted o-phenylene group is a halogen atom, a nitro group, an alkyl group, a carboxyl group, an amyl group or an aryl group.

14. A process of forming positive images as set forth in claim 7 wherein the bismuth compound is an inorganic bismuth compound.

. mercaptobenzimidazole,

15. A process of forming positive images as set forth in claim 14 wherein the inorganic bismuth compound is substantially completely soluble in water.

16. A process of forming positive images as set forth in claim 1 wherein the silver halide is present in an hydrophilic binder.

17. A process of forming direct positive images which comprises subjecting a light developable gelatin silver halide light-sensitive photographic material comprising silver halide grains of a mean grain size of less than 5 microns having occluded therein from 5 X 10 to 10 mole percent, per mole of silver halide, of at least one bismuth compound, and containing at least one mercaptan compound in an amount of from 0.05 to 25 mole percent, based on the moles of silver halide, to an imagewise exposure at a total time 10' to 10 seconds and at 15,000 lux to 10 lux, and then subjecting the material to an overall exposure at an exposure greater than 54,000 CMS but less than about 10 CMS, whereby imagewise unexposed areas are selectively colored by printing out upon overall exposure to yield the positive image, said mercaptan compound having the formula:

wherein X represents an oxygen atom, a sulfur atom, a selenium atom, or -NR R and R each represents a hydrogen atom, a halogen atom, a nitro group, an alkyl group, a substituted alkyl group, a carboxyl group, an acyl group, an aryl group, an alkoxyl group, an alkoxycarbonyl group, a sulfo group, an o-phenylene group, or a substituted o-phenylene group; and R represents an alkyl group, a substituted alkyl group, or an aryl group, wherein the substituted or unsubstituted alkyl group, alkoxy group, acyl group and alkoxy carbonyl group has from 11 2 carbon atoms, and the substituent on the substituted alkyl group and substituted ophenylene group has a Hammetts substituent constant of from 0.680 to +1.30.

18. A process of forming positive images as set forth in claim 17 wherein the bismuth compound is from the group bismuth nitrate, bismuth sulfate, bismuth oxide, bismuth chloride, bismuth bromide, and bismuth iodide, and the mercaptan compound is from the group Z-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzoselenazo]e, 2-mercapto-4-methylbenzimidazole, Z-mercapto-l ,2- naphthoimidazole, 2-mercapto-5- methylbenzimidazole, 2-mercaptol methylbenzimidazole, 5-chloro-2- 5-carboxy-2- Z-mercapto-S-t- 2-mercapto-5- 2-mercapto-5- 2-mercapto-4- 2-mercapto-6- mercaptobenzimidazole, octylbenzothiazole,

dodecylbenzothiazole, nitrobenzimidazole,

methylbenzothiazolc,

methylbenzothiazolc, 6-ethyl-2-mercaptobenzothiazole, 2-mercapto-4,6-dimethylbenzothiazole, 6- fluoro-2-mercaptobenzothiazole, 6-chloro-2-mercaptobenzothiazole, 4-bromo-Z-mercaptobenzothiazole, 6-iodo-Z-mercaptobenzothiazole, 2-mercapto-6- nitrobenzothiazole, 6-ethoxy-2-mercaptobenzothiazole, 6-chloro-4-methyl-2-mercaptobenzothiazole, -chlor0-2-mercapto-6-nitrobenzothiazole, S-chloro-Z- mercapto-6-nitrobenzothiazole, 6-phenyl-2-mercaptobenz'othiazole, 2-mercapto-5-methylbenzoxazole, 2- mercapto-4,6-dimethylbenzoxazole, 5-chloro-2-mercaptobenzoxazole, 5-phenyl-Z-mercaptobenzoxazole, Z-mercapto-S-nitrobenzoxazole, and 2-mercapto-5- sulfobenzimidazole.

19. A process of forming positive images as set forth in claim 18 where the silver halide: gelatin weight ratio, silver halide expressed as silver, is from 0.2 to 8.

20. A process of forming positive images as set forth in claim 19 where between imagewise and overall exposure the element is heated to a temperature of at least 90C for seconds but a temperature less than 250 to 280C for 90. to 60 seconds.

21. A process of forming positive images as set forth in claim 1 wherein X is oxygen.

22. A process of forming positive images as set forth in claim 1 wherein X is sulfur.

23. A process of forming positive images as set forth in claim 1 wherein X is selenium.

24. A process of forming positive images as set forth in claim 1 wherein X is -NR, where R represents a hydrogen atom, an alkyl group, a substituted alkyl group or an aryl group.

25. A process of forming positive images as set forth in claim 1 wherein the bismuth compound has a watersolubility greater than 10 mole/liter at pH 2.

26. A process of forming positive images as set forth in claim 1 wherein:

the bismuth compound has a water-solubility greater than 10 mole/liter at pH 2 and is present in an amount of 10 to 2.5 mole percent per mole of silver halide; the mercaptan compound is present in an amount of from 0.05 to 25 mole percent based on the silver halide in the silver halide emulsion; where any substituted R or substituted D has a substituent with a l-lammetts substituent constant of from -0.680 to +1.30; the imagewise exposure is greater than 150 CMS', and

the overall exposure is greater than 54,000 CMS.

27. A process of formingpositive images as set forth in claim 17 wherein X is oxygen.

28. The process of forming positive images as set forth in claim 17 wherein X is sulfur.

29. A process of forming positive images as set forth in claim 17 wherein X is selenium.

30. A process of forming positive images as set forth in claim 17 wherein X is NR, where R represents a hydrogen atom, an alkyl group, a substituted alkyl group or an aryl group. l= 

1. A PROCESS OF FORMING POSITIVE IMAGES WHICH COMPRISES SUBJECTING A LIGHT-DEVELOPABLE SILVER HALIDE LIGHT-SENSITIVE MATERIAL HAVING A LAYER OF SILVER HALDE GRAINS HAVING OCCULADED THEREIN AT LEAST ONE BISMUTH COMPOUND AND CONTAINING AT LEAST ONE MERCAPTAN COMPOUND WHICH IS A NON-HALOGEN ACCEPTOR REPRESENTED BY THE FOLLOWING FORMULA TO AN IMAGEWISE EXPOSURE OF A HIGH ILLUMINATION FOR A SHORT PERIOD OF TIME AND THEN SUBJECTING THE SILVER HALIDE LIGHT-SENSITIVE MATERIAL TO AN OVERALL EXPOSURE, WHEREBY IMAGEWISE UNEXPOSED AREAS ARE SELECTIVELY COLORED BY PRINTING OUT UPON OVERALL EXPOSURE TO YIELD THE POSITIVE IMAGE:
 2. A process of forming positive images as set forth in claim 1 wherein said mercaptan compound is represented by the formula:
 3. A process of forming positive images as set forth in claim 1 wherein the exposure time for the imagewise exposure of high illumination is less than 10 2 second.
 4. A process of forming positive images as set forth in claim 1 wherein the amount of the overall exposure is larger than 54,000 CMS.
 5. A process of forming positive images as set forth in claim 1 wherein the amount of said mercaptan compound is from 0.05 to 25 mole percent based on the silver halide in the silver halide emulsion.
 6. A process of forming positive images as set forth in claim 1 wherein the silver halide has a grain size less than about 5 microns.
 7. A process of forming positive images as set forth in claim 5 wherein the bismuth compound is present in an amount of from 10 5 to 2.5 mole percent, per mole of silver halide.
 8. A process of forming positive images as set forth in claim 1 wherein subsequent to imagewise exposure but prior to overall exposure the element is heated at a temperature of at least 70*C for at least 1 second.
 9. A process of forming positive images as set forth in claim 8 wherein the heating is for at least 10 seconds.
 10. A process of forming positive images as set forth in claim 9 wherein the heating is at a temperature less than 250* to 280*C for a time less than 90 seconds to 60 seconds.
 11. A process of forming positive images as set forth in claim 1 wherein the silver halide comprises at least 50 percent silver bromide.
 12. A process of forming positive images as set forth in claim 1 where any substituted R or substituted D has a substituent with a Hammetts substituent constant of from -0.680 To +1.30.
 13. A process of forming positive images as set forth in claim 2 wherein the substituent on the substituted alkyl group is a halogen atom, an acyl group, an aryl group or an alkoxyl group, and the subsituent on the substituted o-phenylene group is a halogen atom, a nitro group, an alkyl group, a carboxyl group, an amyl group or an aryl group.
 14. A process of forming positive images as set forth in claim 7 wherein the bismuth compound is an inorganic bismuth compound.
 15. A process of forming positive images as set forth in claim 14 wherein the inorganic bismuth compound is substantially completely soluble in water.
 16. A process of forming positive images as set forth in claim 1 wherein the silver halide is present in an hydrophilic binder.
 17. A process of forming direct positive images which comprises subjecting a light developable gelatin silver halide light-sensitive photographic material comprising silver halide grains of a mean grain size of less than 5 microns having occluded therein from 5 X 10 2 to 10 1 mole percent, per mole of silver halide, of at least one bismuth compound, and containing at least one mercaptan compound in an amount of from 0.05 to 25 mole percent, based on the moles of silver halide, to an imagewise exposure at a total time 10 9 to 10 2 seconds and at 15,000 lux to 1014 lux, and then subjecting the material to an overall exposure at an exposure greater than 54,000 CMS but less than about 108 CMS, whereby imagewise unexposed areas are selectively colored by printing out upon overall exposure to yield the positive image, said mercaptan compound having the formula:
 18. A process of forming positive images as set forth in claim 17 wherein the bismuth compound is from the group bismuth nitrate, bismuth sulfate, bismuth oxide, bismuth chloride, bismuth bromide, and bismuth iodide, and the mercaptan compound is from the group 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzoselenazole, 2-mercapto-4-methylbenzimidazole, 2-mercapto-1'',2''-naphthoimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercapto-1-methylbenzimidazole, 5-chloro-2-mercaptobenzimidazole, 5-carboxy-2-mercaptobenzimidazole, 2-mercapto-5-t-octylbenzothiazole, 2-mercapto-5-dodecylbenzothiazole, 2-mercapto-5-nitrobenzimidazole, 2-mercapto-4-methylbenzothiazole, 2-mercapto-6-methylbenzothiazole, 6-ethyl-2-mercaptobenzothiazole, 2-mercapto-4,6-dimethylbenzothiazole, 6-fluoro-2-mercaptobenzothiazole, 6-chloro-2-mercaptobenzothiazole, 4-bromo-2-mercaptobenzothiazole, 6-iodo-2-mercaptobenzothiazole, 2-mercapto-6-nitrobenzothiazole, 6-ethoxy-2-mercaptobenzothiazole, 6-chloro-4-methyl-2-mercaptobenzothiazole, 5-chloro-2-mercapto-6-nitrobenzothiazole, 5-chloro-2-mercapto-6-nitrobenzothiazole, 6-phenyl-2-mercaptobenzothiAzole, 2-mercapto-5-methylbenzoxazole, 2-mercapto-4,6-dimethylbenzoxazole, 5-chloro-2-mercaptobenzoxazole, 5-phenyl-2-mercaptobenzoxazole, 2-mercapto-5-nitrobenzoxazole, and 2-mercapto-5-sulfobenzimidazole.
 19. A process of forming positive images as set forth in claim 18 where the silver halide: gelatin weight ratio, silver halide expressed as silver, is from 0.2 to
 8. 20. A process of forming positive images as set forth in claim 19 where between imagewise and overall exposure the element is heated to a temperature of at least 90*C for 10 seconds but a temperature less than 250* to 280*C for 90 to 60 seconds.
 21. A process of forming positive images as set forth in claim 1 wherein X is oxygen.
 22. A process of forming positive images as set forth in claim 1 wherein X is sulfur.
 23. A process of forming positive images as set forth in claim 1 wherein X is selenium.
 24. A process of forming positive images as set forth in claim 1 wherein X is -NR, where R represents a hydrogen atom, an alkyl group, a substituted alkyl group or an aryl group.
 25. A process of forming positive images as set forth in claim 1 wherein the bismuth compound has a water-solubility greater than 10 7 mole/liter at pH
 2. 26. A process of forming positive images as set forth in claim 1 wherein: the bismuth compound has a water-solubility greater than 10 7 mole/liter at pH 2 and is present in an amount of 10 5 to 2.5 mole percent per mole of silver halide; the mercaptan compound is present in an amount of from 0.05 to 25 mole percent based on the silver halide in the silver halide emulsion; where any substituted R or substituted D has a substituent with a Hammett''s substituent constant of from -0.680 to +1.30; the imagewise exposure is greater than 150 CMS; and the overall exposure is greater than 54,000 CMS.
 27. A process of forming positive images as set forth in claim 17 wherein X is oxygen.
 28. The process of forming positive images as set forth in claim 17 wherein X is sulfur.
 29. A process of forming positive images as set forth in claim 17 wherein X is selenium.
 30. A process of forming positive images as set forth in claim 17 wherein X is -NR, where R represents a hydrogen atom, an alkyl group, a substituted alkyl group or an aryl group. 